Tutorial: Memory and Memory Problems WHAT IS MEMORY? Memory is one of the central components of human cognition, including the ability to take in information, process it, store it, and subsequently retrieve it when necessary. Thus the core processes of memory are encoding, storage, and retrieval: Encoding: Processing information, organizing it, and marking it for storage Storage: Holding information over time in what is ideally an organized storage system Retrieval: Calling stored information to consciousness Following TBI, both encoding and retrieval can be significantly impaired. However, storage (i.e., keeping information in storage after it has been effectively processed) is often relatively spared. Therefore, if information can be effectively processed and encoded, it is more likely to be retained, even though it may be difficult to retrieve. Video Illustration of Types of Retrieval Memory Processes and Systems Authorities on memory typically explain human memory by drawing a variety of distinctions among different types or aspects of memory. Understanding many of these distinctions is important for staff and family members working with students with memory and learning impairments. Voluntary and involuntary memory: Encoding: Encoding of information for storage in long-term memory can be either involuntary (incidental, implicit) or voluntary (effortful, deliberate, strategic). Involuntary encoding occurs when the goal of the activity is something other than memory or learning, and memory occurs as a bi-product. For example, a young student may remember the names of geometric figures not by trying to memorize them, but rather because he was involved in an art project in which it was important to process the names of the geometric figures in order to complete the project. Young children tend to be good at involuntary or implicit encoding and weak at voluntary or effortful encoding. Voluntary or effortful encoding occurs when the goal of the task is to learn or remember (i.e., trying to learn or remember). The procedures used to achieve success in effortful encoding tasks are memory strategies (e.g., mentally rehearsing, organizing, or elaborating). Young children as well as individuals with frontal lobe injury tend to be weak at effortful or strategic memory/learning tasks. have or does not know how to use the strategies tha Voluntary and involuntary memory: Retrieval: Retrieval can also be involuntary (often referred to as implicit retrieval) or voluntary (effortful, deliberate, strategic). Involuntary or implicit retrieval occurs when stored information is brought to consciousness with no effort to retrieve the information and often with no awareness that the information was stored. The information may be retrieved automatically when a cue triggers it. Voluntary, effortful, or strategic retrieval occurs when there is an attempt to retrieve the information, that is trying to remember. Young children (e.g., preschoolers) rarely benefit from the s for this purpose. The same is true of developmentally young children and many children with frontal lobe injury. Voluntary retrieval is impaired by damage to the frontal lobes, common after TBI. Involuntary or implicit retrieval may be relatively intact even in the presence of damage to the frontal lobes and to the hippocampus (one of the primary brain structures for human memory and part of the limbic system located in the medial temporal lobes of the brain). See Tutorial on Retrieval and Retrieval Problems. 57 www.projectlearnet.org Retrospective and prospective memory: Retrospective memory is memory for past events. Prospective memory is memory for events in the future (e.g., remembering appointments; remembering to do an assignment). Both types of memory can be impaired by TBI, with prospective memory negatively affected by frontal lobe injury. Verbal and nonverbal memory: Verbal memory is memory for language events or events encoded in language. Nonverbal memory is memory for events not encoded in language. Verbal memory tends to be impaired by damage to language centers of the brain, typically in the left hemisphere. Nonverbal memory may be relatively impaired by damage to the right hemisphere. Sensory modality-specific memory: Memory can also be related to each of the senses (vision, hearing, touch, smell, and taste), with specific memory stores affected by damage to that sensory system. In addition to these memory processes, memory can be understood by distinguishing a variety of memory systems in the brain: Sensory, short-term, and long-term storage systems: In the past, it was common to distinguish three types of memory based on length of time the memory was stored. Sensory store refers to the very brief time that a sensation remains available to sensory consciousness. Short-term store refers to the period of time, from seconds to a few minutes, that information remains in consciousness, depending on efforts (e.g., mental rehearsal) to keep it in consciousness. Short-term storage is said to be limited in capacity (e.g., 7 plus or minus 2 units of information at one time in normal older children and adults). Long term store refers to the extended possibly indefinite storage of information in the knowledge base. Capacity of long-term storage is unlimited. Authorities often maintain that short- term storage is physiologically an electrochemical process whereas long-term storage requires protein synthesis for maintenance of information over extended periods of time. Working memory and the knowledge base: In recent years, the concept of short-term memory has largely been replaced by that of working memory. Working memory refers not just to a holding space (like short- term memory), but rather to the processes used to hold information in consciousness and actively attend to it, filter out that which is irrelevant, and create associations that ultimately assist in transferring information from consciousness to the knowledge base. Therefore, there is conceptual overlap between definitions of working memory, attention, and organization. Working memory enables people to keep one or more thoughts active and possibly to relate the thoughts or create associations. Thus there is a large amount of cognitive activity included within the definition of working memory. Similarly, there is a large amount of brain tissue devoted to working memory tasks, notably dorsolateral prefrontal cortex, both left and right hemispheres. The left hemisphere is associated with manipulation of verbal information and the right hemisphere with visual-spatial information. The long-term storage. Widespread areas of cortex (more posterior than anterior) may be connected in neural networks to support stored memories of people, things, events, or series of events. Declarative and procedural memory: Declarative memory (i.e., remembering or knowing that such and such is the case) is memory for facts of greater or lesser generality (e.g., I remember that George Washington was the first president of the USA; I remember that e=mc2). In contrast, procedural memory (i.e., remembering or knowing how to do something) is memory for procedures that can either be physical acts (like getting dressed or riding a bike) or habits/routines (like preparing toast and eggs for breakfast). After brain injury, declarative memory can be significantly impaired, while procedural memory remains relatively intact. Procedural memory may be relatively intact both in the sense of preserved procedures/routines from before the injury, but also the learning of new procedures, motor acts, or habits. Procedural memory, especially the motor aspects, is said to rely heavily on the basal ganglia and cerebellum. Declarative and 58 www.projectlearnet.org explicit memory systems appear to rely heavily on the hippocampus which is vulnerable in TBI because of hypoxic brain injury (reduction of the supply of oxygen to brain tissue). Explicit and implicit memory: With respect to storage of information, explicit memory refers to memories that are stored along with some awareness that the memory is stored. Implicit memories are stored without an associated awareness that there is such a memory. The explicit/implicit distinction can also be used to refer to encoding rather than storage (explicit = deliberate, voluntary encoding; implicit = involuntary encoding). Finally, the distinction can also be used to refer to retrieval (explicit = deliberate, effortful retrieval; implicit = retrieval with no deliberate attempt to retrieve). After TBI, explicit memory is often impaired while implicit memory may be relatively spared. This is one of the important reasons for using errorless teaching/learning procedures (see below; see Tutorial on Errorless Learning). Implicit memory may be relatively spared because it appears not to be as dependent as explicit memory on the vulnerable hippocampus and prefrontal structures. Emotionally charged implicit memories may rely on the activity of the amygdala, while implicit procedural memories rely on the basal ganglia and cerebellum. Episodic and semantic memory: The knowledge base can be divided into episodic and semantic memories (a subdivision of declarative memory). Episodic memories are those that have a time and place reference in life (e.g., I remember that I lost my wallet at a hotel in Stockholm several years ago). Semantic memories include knowledge of things, events, and concepts that are not tied to my autobiography (e.g., I know that the North won the Civil War). Remote and recent memory: In the context of brain